Neuroradiology

Neuroradiology Indian Medical PG Question 1: A patient presents with fever and a rim-enhancing lesion with an air-fluid level on brain CT. What is the most likely diagnosis?

• A. Glioblastoma
• B. Metastasis
• C. Tuberculoma
• D. Brain abscess (Correct Answer)

Neuroradiology Explanation: ***Brain abscess*** - The presence of **fever** points towards an infectious etiology, and a **rim-enhancing lesion with an air-fluid level** on CT is highly characteristic of a brain abscess. The air-fluid level suggests gas-forming organisms or communication with an air-containing structure like a paranasal sinus. - An abscess is a collection of pus, and the "rim-enhancement" indicates the inflammatory capsule surrounding the infection, while the **air-fluid level** is virtually pathognomonic for an abscess containing gas. *Glioblastoma* - While glioblastoma can be a **rim-enhancing lesion**, it is a primary brain tumor and typically does not present with **fever** or an **air-fluid level**. - It often shows **irregular, thick enhancement** and typically causes significant surrounding edema, but the key differentiating factors here are the fever and air-fluid level. *Metastasis* - Brain metastases often present as **multiple, rim-enhancing lesions**, but they are tumors and do not typically cause **fever** (unless very large with extensive necrosis) or exhibit **air-fluid levels**. - The clinical context (e.g., history of cancer) would be important for metastasis, but the **air-fluid level** strongly differentiates this case. *Tuberculoma* - A tuberculoma is a **granulomatous lesion** that can also show **rim enhancement**, especially with central caseous necrosis. However, it typically does not present with an **air-fluid level**. - While fever can be present in tuberculosis, the **air-fluid level** is the most discriminating feature pointing away from tuberculoma and towards an abscess.

Neuroradiology Indian Medical PG Question 2: A lady presented with a 4 cm tumor in the left parietal lobe for which she underwent surgery and radiotherapy. After 3 months she presented with headache and vomiting. Which of the following would characterize the lesion in the patient?

• A. Digital subtraction angiography with dual source CT scan
• B. Gd-enhanced MRI
• C. 99Tc-HMPAO SPECT brain
• D. 18FDG PET Scan (Correct Answer)

Neuroradiology Explanation: ***18FDG PET Scan*** - This patient, presenting with new neurological symptoms after **surgery and radiotherapy** for a cerebral tumor, faces a diagnostic dilemma: differentiating between **tumor recurrence** and **radiation necrosis**. - **18FDG PET scans** effectively distinguish between these two conditions because viable tumor cells exhibit high metabolic activity and thus actively take up **fluorodeoxyglucose (FDG)**, while radiation necrosis is metabolically inactive and shows little to no FDG uptake. *Digital subtraction angiography with dual source CT scan* - **Digital subtraction angiography (DSA)** is primarily used to visualize **vascular structures** and is not the modality of choice for differentiating tumor recurrence from radiation necrosis. - A **dual-source CT scan** is useful for rapid imaging and dynamic studies but lacks the metabolic information needed for this specific differentiation. *Gd-enhanced MRI* - While **Gd-enhanced MRI** is excellent for detecting **structural changes** and **blood-brain barrier disruption**, it often cannot definitively differentiate between **tumor recurrence** and **radiation necrosis**. - Both conditions can present with similar **enhancement patterns** on MRI, making differentiation challenging without additional metabolic information. *99Tc-HMPAO SPECT brain* - **99mTc-HMPAO SPECT** measures **regional cerebral blood flow (rCBF)**, which can be altered in both tumors and areas of radiation injury. - However, it does not provide the specific metabolic information (glucose metabolism) needed to reliably distinguish between **viable tumor cells** and **radiation necrosis** as effectively as FDG PET.

Neuroradiology Indian Medical PG Question 3: Which imaging modality is most sensitive for detecting early ischemic stroke?

• A. Ultrasound
• B. PET scan
• C. CT
• D. MRI with DWI (Correct Answer)

Neuroradiology Explanation: ***MRI with DWI*** - **Diffusion-weighted imaging (DWI)** within an MRI scan is highly sensitive in detecting **cytotoxic edema** within minutes of **ischemic stroke** onset. This makes it crucial for early diagnosis and treatment decisions. - DWI can identify areas of restricted water diffusion, which is a hallmark of acute cellular injury due to **ischemia**, even before changes are visible on conventional T1 or T2-weighted MRI sequences. *CT* - While frequently used in acute stroke settings, **non-contrast CT** is primarily used to **rule out hemorrhagic stroke** and may only show subtle or no signs of acute ischemia in the first few hours. - Early ischemic changes on CT, often referred to as the **"ischemic penumbra"**, may appear hours after stroke onset, making it less sensitive for very early detection compared to DWI. *Ultrasound* - **Transcranial Doppler (TCD) ultrasound** can evaluate blood flow velocities in intracranial arteries and detect stenoses or occlusions but is not a primary imaging modality for directly visualizing brain parenchymal ischemia. - Cervical ultrasound (e.g., **carotid duplex**) assesses extracranial vessels but cannot directly detect **ischemic changes** within the brain tissue itself. *PET scan* - **PET (Positron Emission Tomography)** can assess brain metabolism and blood flow but is typically not the preferred or most sensitive modality for **early detection of acute ischemic stroke** due to its complexity, cost, and limited availability in emergency settings. - PET is more commonly used in research or for assessing chronic conditions and **metabolic abnormalities**, rather than acute stroke diagnosis.

Neuroradiology Indian Medical PG Question 4: A man presents to the emergency department with a head injury following a vehicular accident. What is the investigation of choice?

• A. MRI
• B. CECT
• C. NCCT (Correct Answer)
• D. X-ray

Neuroradiology Explanation: ***NCCT*** - **Non-contrast Computed Tomography (NCCT)** of the head is the **investigation of choice** for acute head trauma due to its rapid acquisition, wide availability, and excellent sensitivity for detecting acute hemorrhage, fractures, and mass effects. - It rapidly identifies life-threatening conditions such as **epidural, subdural, and intracerebral hemorrhages**, which require immediate intervention. *MRI* - **MRI** is superior for detecting subtle brain tissue injuries, diffuse axonal injury, and non-hemorrhagic lesions but is generally **not the first-line investigation** in acute trauma due to longer scan times, limited availability in the emergency setting, and inability to detect acute hemorrhage as clearly as CT. - Its use is typically reserved for follow-up studies or when CT findings are inconclusive or specific soft tissue detail is required. *CECT* - **Contrast-enhanced CT (CECT)** of the head is reserved for specific indications like evaluating vascular lesions (e.g., aneurysms, arteriovenous malformations) or tumors, which are generally **not the primary concern** in the initial assessment of acute head trauma. - Administering contrast agents can delay imaging, may pose risks to patients with renal impairment or allergies, and does not significantly improve the detection of acute traumatic hemorrhage compared to NCCT. *X-ray* - **X-rays** of the skull are useful for detecting **skull fractures**, but they provide **limited information** regarding intracranial injuries or soft tissue damage, which are critical in head trauma. - They have largely been superseded by CT scans, which offer a more comprehensive view of both bony structures and intracranial contents.

Neuroradiology Indian Medical PG Question 5: A woman presenting with abrupt onset of "the worst headache of her life" Which is the best investigation?

• A. Vessel carotid Doppler
• B. NCCT of the head (Correct Answer)
• C. No imaging
• D. MRI

Neuroradiology Explanation: ***NCCT of the head*** - A **non-contrast CT scan of the head** is the immediate and most appropriate first imaging study for a suspected **subarachnoid hemorrhage (SAH)**, often presenting as the "worst headache of her life" [1]. - It can rapidly detect blood in the **subarachnoid space** with high sensitivity, particularly within the first 6-12 hours of symptom onset [1], [2]. *Vessel carotid Doppler* - **Carotid Doppler ultrasound** is primarily used to assess **carotid artery stenosis** or dissection, which would not be the initial investigation for a sudden severe headache [2]. - It does not visualize intracranial blood or vascular abnormalities within the brain parenchyma or subarachnspace. *No imaging* - Given the severe, abrupt onset "worst headache of her life," **subarachnoid hemorrhage (SAH)** is a critical differential, making no imaging an inappropriate and potentially dangerous choice. - Delaying imaging could lead to severe neurological consequences if SAH is missed. *MRI* - While **MRI** can detect SAH, it is generally less accessible, takes more time to perform, and is less suitable for the initial rapid assessment of **acute SAH** compared to NCCT [3]. - **MRI** is often used for follow-up evaluation or when CT findings are equivocal, but not as the first-line emergency investigation.

Neuroradiology Indian Medical PG Question 6: In which of the following conditions is Stereotactic Radiosurgery primarily indicated?

• A. Ependymoma
• B. Arteriovenous malformation of the brain (Correct Answer)
• C. Medulloblastoma of the spinal cord
• D. Glioblastoma multiforme

Neuroradiology Explanation: ***Arteriovenous malformation of the brain*** - **Stereotactic Radiosurgery (SRS)** is a highly effective treatment for brain AVMs, particularly those that are **small to medium-sized** and located in eloquent brain regions. - SRS delivers a **highly focused dose of radiation** directly to the AVM, causing the abnormal blood vessels to gradually close off over time, reducing the risk of hemorrhage. *Medulloblastoma of the spinal cord* - Medulloblastoma is a **highly aggressive malignant brain tumor** that often metastasizes to the spinal cord via cerebrospinal fluid. - Treatment for spinal medulloblastoma typically involves **cranio-spinal irradiation with chemotherapy**, and SRS is generally not the primary treatment modality for diffuse spinal disease. *Ependymoma* - Ependymomas are tumors arising from the **ependymal cells** lining the ventricles and spinal cord. - While surgery is the primary treatment, radiotherapy, including **conventional fractionated external beam radiation**, is often used as adjuvant therapy, but SRS is less commonly the sole primary indication. *Glioblastoma multiforme* - Glioblastoma multiforme (GBM) is the **most aggressive primary brain tumor** and is typically treated with **maximal surgical resection followed by concurrent chemoradiotherapy**. - While SRS may be used in carefully selected cases for **recurrent GBM** or as a boost in primary treatment, it is not the primary solitary indication for initial management.

Neuroradiology Indian Medical PG Question 7: Most specific finding of acute stroke on CT

• A. Sulcal effacement
• B. Hyperdense MCA sign (Correct Answer)
• C. Mass effect
• D. Loss of gray-white differentiation

Neuroradiology Explanation: ***Hyperdense MCA sign*** - The **hyperdense middle cerebral artery (MCA) sign** is a direct visualization of a **thrombus** within the MCA, making it highly specific for an acute ischemic stroke caused by large vessel occlusion. - This sign indicates an acute arterial occlusion, which is key to early diagnosis and determining eligibility for **thrombolytic therapy**. *Sulcal effacement* - **Sulcal effacement** (loss of the normal grooves in the brain surface) may be an early sign of **brain edema** secondary to ischemia. - However, it is a non-specific finding and can be seen in other conditions causing brain swelling, such as trauma or infection. *Mass effect* - **Mass effect**, such as midline shift or effacement of ventricles, typically occurs later in the course of a large ischemic stroke due to significant edema. - In the acute phase, especially within the first few hours, mass effect is usually not evident, and its presence might suggest a different pathology or a more advanced stroke. *Loss of gray-white differentiation* - **Loss of gray-white differentiation** is an indirect sign of early cerebral ischemia, reflecting developing cytotoxic edema in the affected brain tissue. - While an important early indicator, it is less specific than the hyperdense MCA sign, as various acute brain injuries can cause similar changes.

Neuroradiology Indian Medical PG Question 8: A 40-year-old male presents with a history of headaches, fever, and new-onset seizures. An MRI of the brain is performed, revealing a ring-enhancing lesion with central restricted diffusion on diffusion-weighted imaging (DWI). What is the most likely diagnosis?

• A. Glioblastoma multiforme
• B. Metastatic brain tumor
• C. Brain abscess (Correct Answer)
• D. Toxoplasmosis

Neuroradiology Explanation: ***Brain abscess*** - A **ring-enhancing lesion** with **central restricted diffusion** on DWI is highly characteristic of a brain abscess, due to the presence of pus containing densely packed inflammatory cells and bacteria with high viscosity. - The clinical presentation of **headaches, fever**, and **new-onset seizures** is consistent with an infectious process and increased intracranial pressure. - This combination of imaging and clinical features is pathognomonic for pyogenic brain abscess. *Glioblastoma multiforme* - While GBM can present with **ring-enhancing lesions** and seizures, it typically exhibits **facilitated diffusion** (high ADC values) on DWI due to necrotic tumor core, not restricted diffusion. - GBM is a highly infiltrative tumor with extensive **vasogenic edema**. - Fever is uncommon in GBM unless there is secondary infection. *Metastatic brain tumor* - Metastatic lesions can be **ring-enhancing** and cause seizures, but **restricted diffusion** is not typical unless there is acute hemorrhage or superimposed infection. - The presence of **fever** points away from uncomplicated metastasis. - Multiple lesions at the gray-white matter junction are more typical of metastases. *Toxoplasmosis* - Toxoplasmosis in **immunocompromised individuals** (HIV/AIDS with CD4 <100) causes **multiple ring-enhancing lesions** with predilection for basal ganglia. - Restricted diffusion is **not consistently seen** with toxoplasmosis, unlike pyogenic abscesses. - The specific DWI finding of central restricted diffusion makes brain abscess the most definitive diagnosis.

Neuroradiology Indian Medical PG Question 9: A patient presents with seizures that were controlled with midazolam. Lumbar puncture (LP) revealed no pathology. What is the confirmatory test in the condition shown in the MRI below?

• A. PET scan
• B. CBNAAT
• C. MR spectroscopy (Correct Answer)
• D. MRI serial scan

Neuroradiology Explanation: ***MR spectroscopy*** - The MRI shows multiple **ring-enhancing lesions**, which, combined with the history of seizures and normal LP, strongly suggests **neurocysticercosis**. - **MR spectroscopy** can detect the specific biochemical markers (e.g., lactate, succinate) within the cyst, which are indicative of the parasitic infection, and can help differentiate it from other lesions like tumors or abscesses. *PET scan* - A **PET scan** primarily assesses metabolic activity and is more commonly used in the evaluation of tumors or neurodegenerative diseases. - It is generally not the primary or confirmatory test for neurocysticercosis, as it does not directly visualize the parasite or its specific biochemical markers. *CBNAAT* - **CBNAAT (Cartridge-Based Nucleic Acid Amplification Test)** is a rapid molecular test primarily used for the diagnosis of **tuberculosis**, not neurocysticercosis. - While tuberculosis can cause CNS lesions, the clinical and imaging presentation (multiple ring-enhancing lesions) is more suggestive of neurocysticercosis, and CBNAAT would not confirm this diagnosis. *MRI serial scan* - **Serial MRI scans** are useful for monitoring the progression or resolution of lesions over time, especially in response to treatment. - However, a serial scan is not a "confirmatory test" for the initial diagnosis; it provides prognostic or follow-up information rather than confirming the etiology.

Neuroradiology Indian Medical PG Question 10: Parameningeal Rhabdomyosarcoma is best diagnosed by:

• A. MRI (Correct Answer)
• B. CT Scan
• C. SPECT
• D. PET

Neuroradiology Explanation: ***MRI*** - **Magnetic Resonance Imaging (MRI)** provides excellent soft tissue contrast, which is crucial for visualizing the extent of **parameningeal rhabdomyosarcoma** and its relationship to critical structures like the **meninges**, **brainstem**, and **cranial nerves**. - It is superior for detecting **intracranial extension**, **bone erosion**, and assessing response to treatment, making it the preferred imaging modality for diagnosis and staging. *CT Scan* - **Computed Tomography (CT) scans** are good for evaluating bone involvement and calcifications but offer less detailed soft tissue resolution compared to MRI. - While it can identify large masses, it may miss subtle extensions or involvement of the **meninges** that are readily seen on MRI. *SPECT* - **Single-Photon Emission Computed Tomography (SPECT)** is a nuclear medicine imaging technique primarily used to assess organ function and blood flow, often in cardiology or neurology for functional studies. - It provides limited anatomical detail for the precise localization and characterization of soft tissue tumors like **rhabdomyosarcoma**. *PET* - **Positron Emission Tomography (PET) scans** are excellent for detecting metabolically active tumors, assessing disease burden, and identifying distant metastases, especially when combined with CT (**PET/CT**). - However, while useful for staging and follow-up, it does not provide the high-resolution anatomical detail of the primary tumor's local extent and its relationship to adjacent structures as effectively as **MRI**.

Neuroradiology Flashcard 1 of 10

Question: In _____ imaging, CSF is dark/hypointense and white matter is dark, grey matter is white

Answer: FLAIR

Neuroradiology Flashcard 2 of 10

Question: Dawson fingers are a radiographic feature typically seen in _____

Answer: multiple sclerosis (MS)

Neuroradiology Flashcard 3 of 10

Question: _____ provides a superior definition of the relationship of the glomus tumor to adjacent vascular and skull base structures.

Answer: Gadolinium-enhanced MRI

Neuroradiology Flashcard 4 of 10

Question: What sign on MRI helps establish that the intracranial mass is extra-axial?_____

Answer: CSF vascular cleft sign

Neuroradiology Flashcard 5 of 10

Question: MRI in _____ CJD show abnormalities in caudate or putamen nucleus on FLAIR imaging

Answer: familial (subtype)

Neuroradiology Flashcard 6 of 10

Question: _____ peak in magnetic resonance (MR) spectroscopy is diagnostic of Canavan disease

Answer: NAA

Neuroradiology Flashcard 7 of 10

Question: _____ peak in magnetic resonance (MR) spectroscopy is diagnostic of glioma

Answer: Choline

Neuroradiology Flashcard 8 of 10

Question: _____ is an MRI based neuroimaging which makes it possible to estimate the location, orientation and anisotropy of the brains white matter tracts

Answer: Diffusion tensor imaging

Neuroradiology Flashcard 9 of 10

Question: First Aid Neurology:: Cranial Nerves Pseudotumor Cerebri (aka Idiopathic Intracranial Hypertension) causes a palsy of what oculomotor nerve? _____

Answer: CN VI

Neuroradiology Flashcard 10 of 10

Question: CT scan shows a concavo-convex-shaped hematoma is suggestive of a _____ hematoma

Answer: subdural